I've got about a 125,000 miles on a Sun Valley (located in the Burbank Area) rebuild for my 300sdl. I just drove over there and they swapped out my original trans that was leaking oil from the front pump seal and flaring between shifts. They performed the swap while I waited (approx. 2 1/2 hrs).
Just turned over 400,xxx miles....shifts great and no leaks. Cost me about $1,400...well worth it. Hassel Free
P.S. while I was there waiting for the install I saw two guys that I think were pro ball players (deep pockets) bring their really vintage cherry MB's in for transmissions. I imagine they could have gone anywhere but chose Sun Valley. Also don't let the area unnerve you....old time salvage yards.